The invention described herein was assigned to the United States Government and may be manufactured and used by or for the Government of the United States for governmental purposes without the payment of any royalties thereon or therefore.
1. Field of the Invention
The present invention is directed to a magnetic symbology reader, and more particularly, to an improved method and device for utilizing magneto-optic imaging techniques.
2. Description of the Related Art
Automatic identification comes in many forms, the most familiar being bar coding because it is seen by the general population daily at retail outlets. Bar coding is generally applied on a product label or with a sticky label. Other types of automatic identification are used when the mark is desired on the surface of the product (direct part marking), thereby eliminating the label. Identification symbols marked on parts are visible and are read with CCD devices and decoded.
Direct part marking for automatic identification has evolved to the point that optically visible marks are no longer the only option. The use of special substances in additive marks (those that are applied to the substrate that combine metallurgically and rest on or above the substrate) is a new field of use for 2-dimensional identification symbols. In this case marking material is combined with magnetic substances that are detectable using magneto-optic sensors. These sensors are integrated with the decoding device to form a magnetic symbology reader. These magnetic marks are detectable and decodable through paint and other coatings.
U.S. Pat. No. 5,742,036, incorporated by reference, shows a method of marking, capturing and decoding machine readable matrix symbols utilizing magneto-optic imaging techniques. The magneto-optic imaging apparatus disclosed in that reference has omissions which renders the magneto-optic portion of the apparatus inoperable. Accordingly the present invention rectifies these limitations. This is a necessary modification of the referenced patent for this device to be commercially viable.
An object of the present invention is to correct certain limiting aspects of U.S. Pat. No. 5,742,036 so as to provide an improved method and apparatus for reading and decoding machine-readable, but hidden, matrix symbol markings as well as other 2-dimensional identification symbols on substrate materials.
Another object of the present invention is to provide a method and apparatus for reading/decoding machine-readable-matrix symbols covered or obscured by, for example, paint. These obscured symbols contain magnetic material so as to render them visible to the magneto-optic sensor.
Another object of the present invention is to provide magnetic symbology reader which utilizes polarized light in conjunction with a magneto-optic sensor.
Accordingly, a magnetic symbology reader of the preferred embodiment utilizes a magneto-optic sensor in conjunction with a number of other elements which are necessary for the successful operation of the reader. Specifically, the reader has a source of polarized light contained therein which is directed through the magneto-optic sensor onto a reflector. The reflector reflects the polarized light back through the sensor to the symbol reader camera, and preferably to a view finder camera as well. Note that in principle a single camera with proper interfacing to the decoder circuitry and a Liquid Crystal Display (LCD) is possible. This would eliminate the need for a second viewfinder camera as in the preferred embodiment. The camera or cameras in all embodiments of the invention are equipped with polarizing analyzers so as to form magneto-optic images, and maximize dark-light contrast of magneto-optic images of magnetic symbology. In the event that magnetic fields associated with a magnetic symbol are not detected by the magneto-optic sensor, it is desirable for the light to pass through the sensor and analyzer substantially unimpeded. The analyzer is adjusted accordingly. Additionally, a bias/erase coil is provided proximate to the magneto-optic sensor to provide a way to adjust the effective sensitivity of the sensor.
The magneto-optic sensor produces an image thereon in the presence of a magnetic field which is perpendicular to the magneto-optic sensor so as to provide a visual representation of a magnetic field encountered by the sensor. The cameras visually record that image and while the view finder camera directs the image to a viewfinder, the symbol reader camera provides the visual image data to a symbol processor which decodes the magnetic symbology.